Designs for more than two dozen advanced weapons systems have been compromised by hackers, according to a report prepared for the Pentagon. The hackers are said to be Chinese.

Designs for more than two dozen advanced weapons systems have been compromised by hackers, according to a report prepared for the Pentagon.

A previously undisclosed section of a report published in January, Resilient Military Systems and the Advanced Cyber Threat, lists systems whose designs were breached. These include, according to the Washington Post, missile systems such as the PAC-3 Patriot surface-to-air missile system and the Aegis system, designed to intercept ballistic missiles, as well as the F-35 fighter. The report was prepared by the Defense Department’s Defense Science Board.

The report did not specify whether the data had been stolen from government, military or private computer systems, but suggested that military officials were “frustrated” with the scale of cyber theft from defense contractors. Unnamed senior military and industry officials, speaking to the Washington Post, said that the attacks were Chinese in origin.

“In many cases, they don’t know they’ve been hacked until the FBI comes knocking on their door,” said an unnamed military official speaking to the Washington Post. “This is billions of dollars of combat advantage for China. They’ve just saved themselves 25 years of research and development.”

The public version of the report said “with present capabilities and technology it is not possible to defend with confidence against the most sophisticated cyber attacks,” and “The cyber threat is… insidious, enabling adversaries to access vast new channels of intelligence about critical U.S. enablers (operational and technical; military and industrial) that can threaten our national and economic security.”